You could be forgiven for not believing that a new project based on the work of Irish poet William Butler Yeats might be the rocking-est, modern-est thing the Waterboys have put out in some 25 years. But it is.

For a moment, leave aside the lyrics — though they’re of course simply masterful, by turns bucolic and then stinging. An Appointment with Mr. Yeats, as fashioned by Waterboys leader Mike Scott and an ever-rotating cast of characters, is easily their least esoteric effort since Fisherman’s Blues. (Fans will remember that 1988 effort also included Scott’s first attempt at combining his sound with Yeats, on “The Stolen Child.”) Back then, as they do here, the group scurried along a fine line between their already-established brand of muscular yet melodic rock, and the country-leaning sounds of traditional Scottish music. Not long after, Scott and Co. would dive head-long into rootsier, folkier styles — and, along the way, became ever more marginalized.

It somehow took a poet — as odd, as un-rock ‘n’ roll, as that sounds — to bring them back into the mainstream. Whatever the inspiration for these songs, An Appointment with Mr. Yeats couldn’t be further away from a dandified recitation. Instead, the album positively charges out with this woolly, almost neanderthal cadence on “The Hosting of the Shee,” plunging listeners into an underworld of warring gods.

Over the course of the next 13 tunes adapted into music by Scott (along with fiddler Steve Wickham, trombonist Blaise Margail and eight other members of what’s become a Waterboys orchestra), they also tear into a bluesy take on “The lake Isle of Innisfree,” complete with this snarling fiddle; and unleash a series of thundering riffs on “September 1913,” an epic retelling of this age-old labor showdown in Dublin. “Politics,” with its Stevie Nicks-ish turn by vocalist Katie Kim, honks with a boozy anger, too.

That said, Scott haven’t lost his ability to work in shadow — stripping himself bare on the poignant “Let the Earth Bear Witness,” allowing “The Faery’s Last Song” to unfold within a diaphanous sense of wonder. And, just as often, the Waterboys simply defy any categorization at all, as on “News for the Delphic Oracle,” which morphs from crepuscular cabaret jazz into an anthematic storm of Celtic longing, and then back again.

That’s unstable dichotomy is something that might have brought a twinkle to the eye of Yeats — who, after all, was both a Catholic turned atheist, and a poet turned political firebrand. There’s this, too: In Scott’s hands, Yeats’ long-ago sentiments crackle with newfound meaning. For instance, on “Sweet Dancer” (which features another remarkable visit from Kim), Scott smartly combines elements of other works by Yeats to make a more effective narrative.

I kept coming back to the scalding “September 1913,” though, as it reanimates the seething anger surrounding the more recent financial meltdown. Who knew Yeats — heck, who knew even if the Waterboys, at this late date — could connect so convincingly?

Nick DeRiso has written for USA Today, American Songwriter, All About Jazz, and a host of others. Honored as columnist of the year five times by the Associated Press, Louisiana Press Association and Louisiana Sports Writers Association, he oversaw a daily section named Top 10 in the U.S. by the AP before co-founding Something Else! Nick is now associate editor of Ultimate Classic Rock.